This invention relates to a tube dispenser used for progressively emptying a tube from one end by applying pressure to the contents of the tube from the other end. The tube may be a soft, flexible tube such as holds toothpaste or shampoo, or may be a tube comprised of a rigid cylinder having a moveable piston therein, such as is used to dispense caulking or glazing compound and the like.
Whether dispensing from a flexible or rigid tube, one problem often encountered in connection with the use of a mechanical tube dispenser or caulking gun is the tendency of the tube to continue to dispense material after each stroke of the dispenser. This is usually caused by an "over-kill" pumping or moving of the dispenser handle in an effort to speed the dispensing of the material from the tube. After the desired amount of material has been dispensed, the pressure inside the tube has not yet equalized so it continues to dispense.
So far as is known, only one type of device--a trigger-type caulking gun--is available which will prevent residual dripping of materials housed in rigid tubes. This involves the incorporation into the caulking gun of an elongate plunger in axial alignment with the tube and having a circular plate on one end which fits into the hollow of the tube and bears against the moveable piston. One side of the plunger is provided with ratchet teeth which correspondingly engage with a ratcheting member connected to the trigger. During each reciprocation of the trigger, the ratchet forces the plunger slightly further into the tube. To prevent dripping and to stop the flow precisely when desired, the plunger is rotated so that the ratchet teeth are moved out of mating engagement with the trigger and pressure on the piston is released. The disadvantage is, of course, that a completely separate movement apart from the actuation of the trigger is required to stop the flow when necessary, followed by a movement of the plunger back into mating engagement with the trigger each time continued dispensing from the tube is desired. Applicant is not aware of any prior art device which permits precise control of dispensing from rigid tubes without the requirement of a completely separate "disconnecting-connecting" movement, as described above.
Likewise, applicant is aware of no prior art device which permits the same precise metering of materials from flexible tubes. Attempts have been made to correct these problems, but without apparent success. For example, the Mirka U.S. Pat. No. 3,417,902 discloses a rather complicated device which utilizes a slidable bar gear operated by a cam which drives a roller which squeezes a tube. Through a complicated mechanism, a plunger automatically interrupts the flow of paste through the discharge port at the bottom end of the dispenser.